Carburetor



w. SCOTT 1,934,240

CARBURETO'R Filed Dec. 26. 1929 Patented Nov. 7, 1933 UNITED STATES PATENT OFFICE Feeding Carburetor Company, Inc., Boston,

Mass., a corporation of Massachusetts Application December 26, 1929 Serial No. 416,411

2 Claims.

This invention relates to self-feeding carburetors for internal combustion engines, and especially, although not exclusively, to carburetors of the type disclosed and claimed in Patent No. 1,749,893, dated March 11, 1930, wherein an air valve is automatically opened by the suction of the engine, as applied thereto under the control of the throttle valve, and itself controls, by its opening and closing movements, the fuel supplied by the fuel nozzle.

The invention has for an object to promote the acceleration or quick pick-up of the engine, which object is accomplished, in part, by providing a construction wherein such factors as might otherwise tend to retard the opening movements of the air valve are reduced to a minimum. In carrying out this object of the invention, means are also provided for automatically injecting an auxiliary supply of fuel into the air passages adjacent the regular fuel nozzle when the throttle valve, and consequently the air valve, is suddenly opened.

Another object of the invention is to provide for an increased range of movement of the air valve under the influence of a given change in intake suction, thereby effecting a more delicate and accurate control of the fuel supply and insuring an adequate supply at all speeds.

The more particular objects of the invention, together with means whereby the latter may be carried into effect, will best be understood from the following description of a preferred embodiment thereof illustrated in the accompanying drawing. It will be understood, however, that the particular construction described and shown has been chosen for purposes of exemplication merely, and that the invention, as defined by the claims hereunto appended, may be otherwise embodied without departure from the spirit and scope thereof.

In said drawing:

Fig. 1 is a vertical section, the parts above the mixing chamber being shown in elevation.

Fig. 2 is a side elevation of the parts at the bottom of the carburetor proper.

Fig. 3 is an enlarged detail section on the line 3 3, Fig. 1.

The carburetor proper comprises a suitable casing within which is located the various instrumentalities for providing a proper fuel mixture. In the present instance, the casing is constructed to provide a mixing chamber 9 and a suitable air intake passage 10, and mounted at the upper end of the casing is a throttle valve 11 controlled in the usual manner by means of a lever 12. At

the base of the mixing chamber 9 there is formed a valve seat 13 and cooperating therewith is a tapered air intake valve 14. 'Ihis valve comprises a vertically disposed valve stem 14a extending downwardly through a boss 15 and secured to the lower end of the valve stem 14a is a piston or plunger 16 which is located within a chamber or cylinder 17 formed in the lower end of the carburetor casing.

The air intake valve 14 is slidingly mounted in the upper end of a hollow boss or bearing 15 communicating at its lower end with a cylinder 17, and is controlled by means of a compression spring 18 surrounding the valve stem 14a and interposed between the upper end of the boss 15 and a collar 16a secured to said valve stem. Suitable ports 19 are provided in the piston 16 for the passage of fuel, and this is regulated by means of a disk valve 20. The valve stem 14a is drilled from top to bottom thereof 'and is provided at its upper end with a spray nozzle 21 having a suitable oriiice 21a. Ports 14b in the wall of the hollow valve stem aiford communication between the fuel nozzle 21 and the interior of the cylinder 17 above the piston 16, whereby as said piston rises with the air valve 14, fuel will be forced or pumped to the fuel nozzle. A Venturi member 30 is secured to the upper end of the valve 14 and is formed adjacent the orifice 21a to provide a Venturi opening or passage 31 constituting a mixing throat, and below this Venturi opening the valve head 14 is provided with a series of air supply ports or passages 31a communicating with the air intake passage 10.

Extending through the vertical bore in the valve stem 14a and the fuel nozzle 21 is a metering pin 22, the lower end of which is pinned to a rack 23. Meshing with this rack is a gear 24 mounted on a rock shaft 25, this shaft extending through the casing and carrying at its outer end a bell crank lever 26. A suitable wire or cable may be connected to the arm 26a of this lever and operated from the dash of the car.l 'I'he other arm' 2Gb of the lever is connected to one end of a tension spring 28, the opposite end of which is connected to a lug 29 formed on the casing. From this construction it will be seen hat by swinging the lever 26 against the tensio of the spring 28 the rack and gear 23, 24 will be operated thereby shifting the metering pin 22 in a vertical direction and regulating the iiow of fuel through` the orifice 21a. 'I'he upper end of the pin 22 is tapered off at opposite sides, as shown at 22a in Fig. 1, so that as the pin is given a vertical movement the size of the orifice 21a is varied.

In the present construction, the wall of the casing is provided with a duct 32 connected by means of a duct 36 with the outlet of the carburetor between the spray nozzle and the intake of the engine. The duct or passage 32 communicates through ducts 32a and 35D with a duct 33 leading into a vacuum chamber 34 at the top of a float chamber or fuel reservoir 35.

The fuel or float chamber 35 is supplied with fuel from a suitable source of supply through a pipe 37 inserted into the upper end of a cap 37a secured by means of screws 38 to the head 39 of the float chamber. As illustrated in Fig. 1, the cap 37a provides a chamber 40 within which is detachably mounted a ring 41 carrying a screen or strainer 42. The head 39 of the fuel chamber is drilled at 43 and counterbored at 44 to provide a seat for a valve 45. Within the fuel chamber is located a fioat 46 which is hinged or pivoted at 47 to the chamber and is so positioned as to cooperate with the lower end of the valve 45. As

the level of :fuel rises or falls within the float chamber, the float 46 will swing slightly on its pivot, thereby controlling the opening and closing of the valve 45 and the flow of fuel into the float chamber. The float chamber communicates with the chamber 17 beneath the piston 16 by means of a passage or duct 48.

The head 39 of the float chamber is provided at its top With a boss 49 drilled to provide a vertical passage 50 and a horizontal communicating port 51 of relatively small size. A screen 52 may be mounted over the boss 49` so as to prevent ingress of foreign particles through the air Vent 51.

It will be noted that the inlet valve 45 is positioned at one side of the center of the fuel chamber and in close proximity to the pivot 47 of the float. The latter acts as a lever to control the opening and closing of the valve, and a firm and steady coaction between the float 46 and valve 45 is obtained without substantial influence from engine or vehicle vibrations.

The operation of the parts as above described is substantially the same as in application Serial No. 230,639 above referred to. When the engine is idling the air intake Valve will be in the position shown in Fig. 1. The engine suction will induce a partial vacuum in the mixing chamber 9 and the vacuum chamber 34 by means of the ducts 32, 33, etc. The flow of fuel to the orifice of the spray nozzle is permitted by the air vent hole 51. Upon opening the throttle additional air is admitted past the valve 14 which will be raised from its seat 13. As the effect of the engine suction on the carburetor increases, due to the opening to the throttle, thereby tending to increase the vacuum in chamber 34, this action will be compensated for by the increased velocity of air through the Venturi opening 31, resulting in increasing the flow of fuel from the spray nozzle. It. Will therefore be seen that by providing the Venturi opening around the fuel nozzle 21 a constant partial vacuum of predetermined amount is maintained within the mixing and float chambers while permitting the proper amount of fuel to be fed from the spray nozzle at varying speeds.

In accordance with the present invention, and for the purpose of promoting the acceleration or quick pick-up of the engine, the boss 15 is provided at its upper end with passages 53 communicating with the interior of the cylinder 17 and directed toward the air valve 14. When the air valve suddenly rises as the result of a sudden opening of the throttle valve l1, and a consequent sudden increase in engine suction as applied to said air valve, the piston 16 forces an auxiliary supply of fuel through the auxiliary fuel nozzle provided by the passages 53, delivering the same to the annular air space between the valve 14 and its seat 13, as well as to the air passages 31a through which latter a portion of said auxiliary supply passes to the mixing throat 31.

For the purpose of preventing undue retardation of the opening of the air valve 14 upon a sudden opening of the throttle valve, and consequent sluggish response of the carburetor to operating conditions, the piston or plunger 16 is slidably mounted on the valve stem 14a and is normally held in engagement with the collar 16a by a spring 54 interposed between said piston and a nut 55 threaded upon the flower end of said valve stem. This construction permits the piston 16 to yield if necessary, so as not to retard the sudden opening of the air valve 14, without however seriously diminishing the flow of fuel to the main fuel nozzle 21, or to the auxiliary fuel nozzle 53, which flow is determined by a strength of the spring 54.

In order to avoid any tendency toward the creation of a vacuum under the piston 16 when the air valve 14 suddenly rises, thereby further preventing retardation of the opening of said valve, the passage 48 leading from the float chamber 35 is made of a size and capacity materially in excess of the requirements of the fuel nozzle at maximum opening, and is controlled by a check valve 56 in order to prevent the piston from forcing fuel back into the float chamber through said enlarged passage upon a sudden descent, thereby insuring the lifting of the valve 20 to pass the fuel into the upper end of the cylinder 17. Since some appreciable force is necessary to open the check valve 56, and in order to avoid and insure against failure of the fuel supply for this reason, or in case of sticking of said check valve, there is. provided about said valve a small by-pass 57 of sufficient capacity to supply the running demands. The by-pass or passage 57 is not, however, large enough tointerfere with the pumping action of the piston 16 when said piston descends upon closing of the air valve.

In carburetors of this general type, wherein the opening of the air valve is effected and controlled by the engine suction and in turn controls the supply of lfuel through the fuel nozzle, difculty has heretofore been encountered in obtaining a sufficiently delicate control of the fuel supply due to the short range of movement of the air valve. Thus, it will be seen that upon an initial lifting of the air valve 14 an annular passage between said valve and its seat 13 is immediately opened. In carburetors of this type as heretofore constructed, said initially opened annular passage has been of sufficient capacity to slow down the further opening of the valve, so that the range of movement of the nozzle 21 with respect to the metering pin 22 has been insufficient to provide for an adequate fuel supply at high speeds unless the tapering 22a of the metering pin were made very abrupt, making it diilicult to effect the necessaryregulation of the fuel supply at low speeds. In` accordance with the present invention this difficulty is overcome by providing a construction which compels an increased range of travel of the air valve for a glven change in engine suction, or which, in other Words, requires a relatively great opening movement of the valve in proportion to the area of the air passage opened by such movement, thereby providing a greater relative movement of the fuel nozzle and metering pin, aifording a more delicate control of the fuel supply, and insuring an adequate supply at all speeds. To this end, in the construction shown, the valve seat 13 is formed with an upwardly flaring annular extension 58 which surrounds the air valve, restricts the annular air passage opened by the initial opening of said valve, and requires the latter to move upwardly a greater distance in order to open an annular air passage suiilcient to supply the increase in suction demand.

The mixing chamber 9 is preferably formed separate from the remainder of the carburetor casing and is secured thereto by bolts 8, while the valve seat 13 and extension 58 are also preferably formed on a separate part or unit 13a provided with a flange 13b which is clamped between the mixing chamber member and the body Vof the casing. It has been found in practice that different engines require, for their most eilicient operation, valve seats having extensions 58 of slightly diierent flare or taper, and the ccnstruction above described permits the valve seat unit to be readily removed for the purpose of replacing the same by another interchangeable unit of slightly different form or of reshaping the extension 58 to give the same the most desirable and enicient operation for the particular engine in which the carburetor is used.

Having thus described my invention, I claim:

1. In `a carburetor for internal combustion engines, in combination, an air valve subjected to engine suction and having a mixing throat therein, a seat for said valve, a fuel nozzle and cooperating metering pin one of which is carried by said air valve, said fuel nozzle communicating with said mixing throat and said air valve having air passages likewise communicating with said mixing throat adjacent said fuel nozzle, means providing an auxiliary fuel passage adapted to deliver fuel to the air space between said valve and its seat and to said mixing throat, and means rendered operative by a substantial increase in the eiect of said suction for causing a ow of fuel through the auxiliary passage.

2. In a carburetor for internal combustion engines, in combination, an air valve subjected to engine suction and having a mixing throat therein, a fuel nozzle and cooperating metering pin one of which is carried by said air valve, said fuel nozzle communicating with said mixing throat and said air valve having air passages likewise communicating with said mixing throat adjacent said fuel nozzle, a cylinder communicating with said fuel nozzle, means for supplying fuel to said cylinder, a piston working in said cylinder and connected with said air valve, and an auxiliary fuel nozzle communicating with said cylinder and arranged to supply fuel to said mixing throat.

WILLIAM SCO'I'I'. 

